Method of making irradiation subdividing screens



Aug. 18, 1935.. L. P. F. VAN DER GRINTEN 2,051,536

METHOD OF MAKING IRRADIATION "SUBDIVIDING SCREENS Original Filed Aug. 3, 1934 Patented Aug. 1936 METHOD or MAKING IBRADIATION SUBDIVIDING SCREENS Lodewiihlieter Frans van der Grinten, Venlo,

Netherlands, assignor to Naamlooze Vennootschap Ohemische Fabriek L. van der Grinten, Venlo, Netherlands, a limited liability company of Netherlands Original application August 3, 1934, Serial No. 738,350. Divided and this application February 8,1935, Serial No. 5,678, and in the Netherlan August 11, 1933 3 Claims. (01. 95- 31 I greater actinic intensity and the average inten- In the production of reflexion copies a process is known according to which the radiation, before its passage through the light-sensitive layer in which the image has to be formed-is subdivided into small regions of greater and of smaller actinic intensity.

This subdivision may be efiected for example by causing the irradiation to take place through a so-called screen which may be provided between the source of radiation and the sensitive sheet,

advantageously in the immediate neighbourhood of the sensitive sheet, possiblyin direct contact therewith. Practically useful screens are not only covering screens, but also lens, prism, or similar screens. The lens, prism, or similar screens are hereinafter called dividing screens.

By the expression dividing screen must therefore be understood any structurethat is pervious to radiation and that intercepts the radiation.

energy lessv than a covering screen when it divides a homogeneous radiation into small regions of greater and smaller activity. i

As materials for making these dividing screens there come into question all materials that are pervious to radiation, as quartz, different sorts .of glass, celluloid, cellulose, cellulose derivatives, gelatine, and the like. The choice of the material is determined, inter alia by the desired index of refraction, by the manner of'makin and oi employment etc.- Materials like celluloid, cellulose, cellulose derivatives, gelatine, and the like, haveior example the advantage that they are unbreakable and can be made into thin foils.

The method with dividing screens has the advantage that, in comparison with covering screens, less of the radiated energy is intercepted.

In the case of dividing screens a considerable portion of the impinging radiation energy is indeed let through and although there is subdivision into small regions of greater and smaller actinic activity the total quantity of the energy let through does not difier considerably fromthe total impinging energy. Dividing screens are consequently preferred in many cases to covering screens.

This application is a division of application Serial No. 738,350ffiled- August 3, 1934. v The present invention relates to irradiation subdividing screens which can advantageously be used in refiectography, and to processes of making same. According to the'invention it has been found that in the case of the method with dividing screens reflexion copies are obtained that are the stronger the greater is the ratio be- (tween; the average intensity of the regions 01 sity of the regions of smaller aetinic intensity. -It is not obvious that this ratio must be relatively great. For, the assumption would have been logical that'a reflexion copy established with application of a subdivision of the irradiation always must be stronger than a reflexion copy ob.- tained without subdivisiomhow small the abovementioned ratio 'in the subdivision might be. This, however, is not the case.

When the above mentioned ratio is insuillcient, generally even worse results are obtained by the process with subdivision than by that without.

subdivision. K

Only when the ratio in the subdivision is sufficiently great better results are obtained by the process-with subdivision than by that without subdivision. v It is also advantageous in general in workin wit-h dividing screens tohave the regions of greater activity or greater intensity. as small as possible.

It .has been found that the effect of a ratio between the pertinent activities of the regions of greater and smaller activity that is as large as possible can be attained by a combination of a.

lens screen with a covering screen, the rays being concentrated for example by the lenses on the pervious parts of the covering screen; The impervious portions intercept the dispersed radiation in the regions of the smaller activity that is caused for example by imperfections of the lenses.

In the case of the employment of the above mentioned combinations of lens-and covering screenings the employment of radiation that is directed as parallelly as possible is desired.

The expression parallelly directed radiation is in reference hereto in this description and in the claims to be understood in a definite wide sense, and indeed, in such a mannerfthat for example a radiation by apunctiform or approximately punctiform. source of light at a distance not considerably greater than the dimensions of the system to be irradiated likewise comes under the expression parallelly directed radiation The rays have then, it is true, at different parts (at a great distance from one another) of the entry'surfa'ce of the system to be irradiated directionsthat differ inter se, but at these parts themselves and in their immediate neighbourhood in the entry surface there are practically only rays of a definite direction. In practice it isin- 'fact without further. means extremely difiicult and in many cases even practically impossible to pro-;

Q ducea perfectly parallelly directed radiation radiation) in practice as a parallelly directed ra-'- diation.

Instead of a punctiform source of radiation there may be advantageously used a linear or band-like source of radiation or a punctiform source of radiation moving rectilinearly, if there is-employed for the production of the reflexion copy a subdivision of the radiation into small regions of greater and less actinic intensity that islinear. In such a case it is advantageous in the employment of the method according to the invention to arrange the linear or band like source of radiation parallelly or approximately parallelly to the lines of the division. In the case of the employment of a linear or band like source of radiation as above mentioned this radiation must be regarded as parallelly directed in the sense of what has beenhereinbefore stated at least in the case of a breadth of theband-like source of light that is relatively not too; great. The rays have then it is true different directions inter se in their .projection on a plane' 10-, cat d perpendicularly to the dividedand linear r us at diflerent lines located at a great-distance from one another of the entry surface of the systemtto be irradiatedbut at these lines themselves and in their immediate neighbourhood in the entry surface there are practically only rays that have a definite direction in the above mentioned projection. 'A particularly good arrangement for what has been .described above, especially for the irradiation of large sur faces, is obtained by giving the surface to be irradiated the form of a circular cylinder, which may mqveor not whilst the source of radiation is located or moves in the axisof the cylinder.

The above-mentioned lens covering screens may is furnished with a, lens be advantageously optaned photochemically from sensitive material whi screenfl J If one starts for example with a positive diazot layer combined with a'cylindrical lens screen and irradiates this system through the lenses on a background that is non-reflective or is reflective as little as possible, the diazo compound is. idecomposed in the focal lines. These conse-,

quentlyremain pervious to radiation, whilst the parts outside the focal lines .become impervious nduring later formation of coloring matter. fI'he is in this case advantageously carried out slowly, or care is taken that the diazo layercontains sufficient moisture and maybe through cooling remains at so low atemperatur'e that the formation of injurious littlebubbles of nitrogen during the irradiation is reduced as much as possible or prevented; Lt instead of thedi'azo layer. is employed :a silver compound layer, a like eflect may be produced byreversing thepicture after the irradiation:

Also, without reversing the compounds, dividing covering screens can be produced by carrying out the irradiation at a definite angle of incidence-or several definite angles of incidence which are. drier-e tfrom the angle of ineidencethat is to be oyed during the use method that comes into question therefor.

picture by means of negatively acting sensitive layeraas of silver',

of the system obtained in this way as il. dividing covering screen.

' Inlthis way the portions of the silver-compound layer that 'are situated outside the fool-or focal lines to be employed later are rendered 5 -covering and consequently intercepting. In

stead of diazo and silver compounds there may of course be employed any other photographic Thus, for example, dividing screens with reflective porlo tions may be obtained by first producing a bichromate gelatine screen and then silvering or nickeling it. (See French Patent Specification 619,719.) Such screens have, in addition to the.

advantages of dividing screens, also the advan- 15 tage of being reflective. Of course one may, without a photochemical method, simply put together a lens or prism screen and a covering screen, but-- the covering portions in the plane of, the foci or focal lines. They may also be placed between the lenses before this plane, and, even, at not too great a distance, behind this plane.

It is, however, advantageous to keep as small as pos- 25 sible the distance between the plane inwhich are located the-coveringportions and that in which are located the foci or focal lines.

-During the production of reflexion copies by means of a lens covering screen obtained photo- --the production of the reflexion copies therewith each part of the entry surface of the lens covering screen is impinged upon by a radiation of the same or approximately the same direction in botlrcases, in both cases inthe definite wide sense as stated above in the explanation of the expression par'allelly directed radiation; but with this exceptionthat if the covering screen is 40 obtained by a photochemical process on a. negative acting layer without reversion-of the negative, there must exist a definite difierence between the direction of the rays in making the covering screen and the direction of the rays inusing the screen. This difference, however, must. be as much aspossible the same in every place of the sheet. I v

This analogy of the two radiations may for example be realized by choosing the system comprising the source of radiation and the surface to be irradiated during the making of the lens covering screen as analogously as'possible to the system that is desired to employ during the sub- .sequent production of the reflexion copies. If,

afterwards, it is desired to produce the reflexion .copy with-a definite angle of incidence, for example, greater than 0, the lens cove in screen required therefor must be'madealso with the same angle of incidence or when usinga negative acting layerwithout reversion with an angle of incidence differing in a definite manner from the angle of incidence employed in the use of the screen. j

The accompanying drawing is a diagrammatic section of a screen according to' the invention showing the path of the light rays.

Example L lens screen LR of size of 20X 30 cm. (seefigure) consisting of an acetyl cellulose foil 0.16

' mm thick which is provided on one side'- with cylindrical lenses having a radius of 0.04 mm and a mutual distance of the focal lines'of-"0.04

sensitive chromate gelatine layer d. Behind the sensitive layer there is an absorbent background A. Irradiation is effected from the lens side by means of an arc lamp without reflector at a distance of about 1 mm at an angle of incidence of Il /2 (this angle of incidence is measured in the -middle of the irradiated system and in a plane perpendicular to theaxes of the lenses). The angle of incidence is chosen on the left or the right in the planethrough the source of radiation perpendicular to the axes of the cylindrical lenses.

After the irradiation the chromate gelatine picture is silvered or nickeled to make it highly l5 reflective.

There is obtained a reflective covering in the parts s. screen obtained forms a specially advantageous combination for the production of reflexion copies. In this production there are advantageously employed sensitive layers of for example a thickness of 0.01 mm or less and irradiation is efiected advantageously by means of a like or analogous system but now with'an angle of incidence of 0. The pencils of rays thenipass through between the parts a The result may be still somewhat improved by effecting the irradiation during the making of the lens covering j mirror screen not with an angle of incidence of exactly 11 but variously with angles of incidence varying between 8 and 15, whereby a larger covering region 1. is produced.

Also,- in the making of the lens covering mirror screen angles of incidence of about'34 about 57, and so on, or varying angles of incidence;

which, as above indicated, are in the neighboura suitable distance.

flexion copies at an angle 01! incidence of 09.

hood of these values, may be employed. Also several sources of radiation may be employed, it

being assumed that their rays impinge at the above mentioned angles of incidence.

the lens screen is provided with a silver bromide layer (asimilar combination is used for color kinematography) there is obtained a non-reflective lens covering screen which likewise gives 45 a clearly better effect in the production of rethe right or the left. After the usual treatments,

as developing; flxing and washing, the'lens covering screen is suitable for the making of re- The lens.covering mirror If in the above mentioned the lens-free side of It is also suitable for the making of reflexion copies at angles oi incidence of 23, 46 and so on, on the right or on the left. Y

When in the making of the lenscovering screen there is used an agle of incidence of 5% on the left, the reflexion copy may be made at an equally great angle of incidence on the right. In the above all the angles of incidence are of course measured in a plane perpendicular to the axes of the screen and also in the middle of the .lens covering screen to be made, or of the system to be copied, at least at the same place of the lens "covering screen, as well during its making as duringits use.

Having fully described the invention, what I a claim asnew and desire to secure by Letters Patent is:

1. A method for preparing screens adapted for use in the making of reflex copies which coinprises subjecting a combination of a lens screen and a negatively working sensitive layer'to a radiation passing first through the lens screen and then impinging upon said layer, said radiation being a directed radiation having an angle of incidence substantially differing from zero,

and developing the sensitive layer to thereby convert said layer into a covering screen whose pervious portions are located substantially perpendicularly under the centre of the lenses.

2. A'method for preparing screens adapted for use in the making of reflex copies which comprises subjecting a combination of a lens screen and a negatively working sensitive layer to a radiation passing first through the lens screen and then impinging upon said layer, .said radiation, being a directed radiation having more than one direction of incidence substantially 'differing. from zero, and developing the sensitive layer to thereby convert said layer into a covering screen whose pervious portions are locatedsubstantially perpendicularly under the centre of the lenses.

3. A method for preparing s creens adapted for I use in the making of reflex copies which comprises subjecting a combination of 'a cylindrical lens screen and a negatively working sensitive layer, to a radiation passing first through'the lens screen and then impinging upon said layer, said radiation being a directed radiation, having directions of incidence which are' directed by the lenses of the lens screen in focal lines located between the planes passing through the axis of the lenses perpendicular to the sensitive layer. LODEWIJK PIETER FRANS I van on GRIN'I'EN. 

